Strength Training Is Not a Luxury. It Is a Necessity.

There is a deeply rooted idea that running is enough. That if you run, you are healthy. That accumulating kilometers is enough to build a functional, resilient, and healthy body for the long term. It is not.

As a strength and running coach, I see the real cost of this belief every day: runners who get injured regularly, who stagnate in their times, and who reach their fifties with compromised knees and bone density that should have been addressed a decade earlier.

The problem is not running. The problem is running without a foundation.

What the science says in 2026
In March 2026, the ACSM, the American College of Sports Medicine, published its biggest update on resistance training in 17 years, based on 137 systematic reviews. The message is clear: resistance training is not a complement. It is a central pillar of adult health.

But in Portugal, the reality is different. People do not live by ACSM recommendations, and that is fine. What matters is what actually reaches them. And what still reaches too many people is the old bodybuilding myth: “If I lift weights, I will get bulky,” “That is for people who compete,” “I just want to run.”

It is getting better. But there is still a lot of work to do.

What your muscles actually do when you run
When your foot hits the ground during running, your body absorbs two to three times your body weight. That impact has to go somewhere.

If your muscles are strong and prepared, they, together with the support of your tendons, absorb and control that load efficiently. Tendons work like elastic springs, storing and returning energy. But the muscles are the main structures responsible for actively absorbing impact.

If they are not prepared, that load is distributed through structures that were not designed to handle it alone: joints, fascia, periosteum, and bone. That is where injuries happen, not because you ran too much, but because you ran without enough preparation.

The three types of contraction your training needs
Strength training is not just one thing. There are three fundamental ways the muscle works:

Isometric: The force you produce matches the resistance. There is no movement. Example: a plank.

Concentric: The force you produce overcomes the resistance. The muscle shortens. Example: the upward phase of a squat.

Eccentric: Gravity is acting and you are slowing the movement down. The muscle lengthens under load. Example: the slow lowering phase of a squat.

Of these three, eccentric work allows the muscle to produce the greatest absolute force, and the 2026 ACSM position stand notes that hypertrophy is enhanced by higher weekly volume and eccentric overload.

A good strength program combines all three. You do not train eccentrics just because ACSM says they matter. You train them because they make physiological sense, and because your body performs eccentric actions every single day, whether you like it or not.

The window of opportunity most people waste
The best time to start strength training is before you start running. The second-best time is today.

Every year that goes by without a strength stimulus is a year in which bone density, muscle mass, and tendon capacity have not improved, or have declined. That cannot be fully undone. It can be minimized, but not erased.

This is not about liking strength training. It is not about motivation, time, or whether the gym feels boring. It is about doing what needs to be done if you want to age with quality of life.

Strength is not just another performance metric. It is a health metric.

Do what needs to be done.